Planet Sudoku

How do you Sudoku? Introduction to How To's

Solving Techniques

Millions of Free Sudoku Puzzles 4x4, 6x6, 8x8, 9x9, 12x12, to 25x25 at Planet Sudoku!

Planet Sudoku's helpers section will improve your puzzle solving skills.

Show Hints / Candidates will help you see the available pencil values within the cell, row, column, and boxes.

Sudoku Solving Methods and Techniques

  • Solving Methods
    • There are two different core methods for solving a puzzle. One is by hint removal / reduction and the other is by solving a cell (entering a penciled value).
  • Solving Techniques
    • There are only two solving techniques for the game of Sudoku, which are NAKED SINGLE, and HIDDEN SINGLE. We will provide additional information later about these techniques.
  • Hint Removal Techniques
    • The other 30+ solving techniques are actually classified as hint removal. They rely on process of elimination logic that removes the possibility of a valid hint from a cell.
  • Difficulty Levels
    • Sudoku puzzle difficulty is not rated based solely on how many open cells there are within the board. More importantly solving techniques define the real difficulty level. There are over 30+ solving techniques ranging from very easy, to insanely hard. We will provide tutorials on the solving techniques we use to build the PlanetSudoku.com Sudoku puzzles.
  • Hint Removal Techniques
    • The other 30+ solving techniques are actually classified as hint removal. They rely on process of elimination logic that removes the possibility of a valid hint from a cell.
  • Difficulty Levels
    • Sudoku puzzle difficulty is not rated based solely on how many open cells there are within the board. More importantly solving techniques define the real difficulty level. There are over 30+ solving techniques ranging from very easy, to insanely hard. We will provide tutorials on the solving techniques we use to build the PlanetSudoku.com Sudoku puzzles.
  • Solving Sudoku Puzzles
    • As mentioned before, there are over 30 different solving methods to complete a Sudoku puzzle. We will be covering some of the most popular solving techniques.
  • Planet Sudoku Solving Engine
    • The solving engine was built completely from scratch (technically more than once).  I read books on these specific solving techniques and applied them to this website. If you feel that you have found a bug within the solving / cell highlighting engine, please feel free to email me. This will help me address any open issues within the system that I am unaware of.
  • Highlighting Engine Legend:
    • Green Highlighter: Valid hints
      Red Highlighter: Invalid hints

Start playing Sudoku online today! We have many different boards and difficulty levels to choose from.